Treatment for improving cellulose insulation

ABSTRACT

A method for manufacturing a tire retardant cellulose insulation with reduced density and reduced settling. The method consists of adding a material, the fibers of which have a positive electrostatic charge, onto a shredded newspaper base either before or after the addition of a pre-coat, consisting of a mixture of limestone and an antistat. A fire retardant agent is then added and the materials are ground in a finish mill. The newspaper fibers become positioned at an angle to the paper pieces, increasing the distance between the paper pieces, thereby lowering the density of the cellulose. Fibers such as ground cardboard, wood mulch, sawdust, and fiberglass fibers are examples of materials with electrostatically positively charged fibers.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. Ser. No. 09/939,178,filed Aug. 24, 2001.

STATEMENT REGARDING FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT

(Not Applicable)

REFERENCE TO AN APPENDIX

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BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to cellulose insulation of the typeutilizing a shredded newspaper base which is treated with a fireretardant chemical composition and used for the thermal insulation ofhomes and other building structures. More particularly, the inventionrelates to the addition of a specific range of antistat andelectrostatically positively charged fibrous materials to the newspaperbase which will lower density and reduce settling of the insulation.

2. Description of the Related Art

The manufacture of cellulosic insulation, in accordance with the presentstate of the art, begins with a grinding operation in which newspapersare shredded to a level of approximately 1″×1″ pieces and individualfibers. These fibers and paper pieces, carried in air stream, are thenground in a second operation in which finely ground fire retardantchemical is added to the paper and paper pieces.

The key to the understanding of the underlying basis of celluloseinsulation is to recognize that cellulose insulation is made up ofnewspaper pieces and fibers which are affected by static electricity.Like elements will repel; unlike elements will attract. A method ofdetermining the electrostatic charge of a material piece or fiber is torub the flat side of a nylon toothbrush about 50 times on a piece ofwool. Then attempt to attract the material in question with the flatside of the toothbrush. If the material is positively charged, it willattach to the flat part of the toothbrush. If the material is negativelycharged, it will not be attracted. Based on the above system, the faceof a newsprint paper piece is positively charged and the edge fibers arenegatively charged. The newspaper separate fibers are also negativelycharged.

U.S. Pat. No. 4,468,336 refers to an insulation “wherein the loose fillcellulose insulation has a settled density on the order of about 2.5pounds per cubic foot before mixing with staple fibers, and the mixtureof cellulosic insulation with from 2% to 25% by weight staple fibers hasa settled density in the order from 2.1 pounds per cubic foot to about1.1 pounds per cubic foot”. Staple fibers were defined as acrylic,polypropylene, acetate etc. These fibers are electrostaticallypositively charged.

Because the paper pieces were positively charged, the surface of thepaper piece attracted negatively charged paper fibers, essentiallyparallel to the face of the paper piece. This attraction caused thepaper piece to become neutrally charged and therefore, no longerstatically attractive. Therefore, the positively charged staple fibersattracted most of the remainder of negatively charged paper fibers,forming a phase separate from the paper pieces. This separate phase isnot settling stable because this structure is not supported by the paperpieces and will condense. It took a large amount of the staple fibers tolower the cellulose density by producing a separate, lower density,paper fiber to positively charged fiber structure.

BRIEF SUMMARY OF THE INVENTION

In an attempt to improve settling and density of cellulose insulation, Idetermined that there was an advantage to produce a specific type offiber-paper piece structure. In this structure, use of thelimestone-antistat mixture as described in U.S. Pat. Nos. 5,399,375 and5,455,065 reduces the static charge on the paper pieces and fibers to alevel where fire retardant chemical will adhere to both the paper piecesand fibers. The preferred structure is where the fibers are attached tothe paper piece at an angle to the face of the paper piece, not parallelto the face of the paper piece. In this preferred structure, there arevery little separate fiber to fiber groupings.

Electrostatically, positively charged fibers, such as wood, orfiberglass added either before or after the addition of the addition tothe partially ground paper, are attracted to the negative edges of theelectrostatically charged paper piece. The attached positively chargedfibers then attract the negatively charged paper fibers, producing areinforced structure which reduces density and settling.

These improvements in density result from the fact that the negativefibers are deposited at an angle to the face of the paper piece. Theamount of electrostatically positively charged fibers added will varywith the type of fiber used. The key is that the amount of separate,positively charged fibers to negatively charged fiber groupings is heldto a minimum.

Additional reduction in settling occurs by increasing the amount ofantistat beyond that amount necessary to produce lower density. Ultimatesettling stability is achieved by reducing the static charges in thecellulose to the point where the cellulose charges are almost neutral.In achieving this reduction in settling, density is increased slightlybecause the electrostatic charges keeping the fibers and paper piecesapart are reduced. Lowering in settling can be accomplished by theaddition of water to the cellulose prior to application, but the levelof settling increases once the water evaporates.

The following convention will be used. Newspaper pieces, wood fibers,cardboard fibers, and fiberglass fibers are positively charged.Newspaper fibers and cardboard pieces are negatively charged. Therelationship of the positively charged fibers to the negatively chargedpaper fibers can only be understood by using a high powered microscope.

In describing the preferred embodiment of the invention, specificterminology will be resorted to for the sake of clarity. However, it isnot intended that the invention be limited to the specific term soselected and it is to be understood that each specific term includes alltechnical equivalents which operate in a similar manner to accomplish asimilar purpose.

DETAILED DESCRIPTION OF THE INVENTION

The amount of wood fiber necessary to reinforce the paper piece/paperfiber structure is in the range of 2% to 8% of the weight of the paperand positive electrostatic fiber input. The amount of fiberglass fiberto reinforce the settling stable structure is in the range of 0.5% to 2%of the paper and positive electrostatic fiber input. The preferredamount of electrostatic positively charged reinforcing fibers isdetermined by the structure achieved, as seen using a high poweredmicroscope.

To reduce density, the antistatic constituent of the precoat mixture ofantistat and finely ground limestone is preferably on the order of0.001% to 0.002% by weight of the sum of the paper and positiveelectrostatic fiber input. Above this level, there will be a slightincrease in density of the cellulose. The limestone component range is1% to 2% of the weight of paper and positive electrostatic fiber input.Other fine ground additives may be used in place of the limestone, butfire retardancy will be decreased. This range of antistat reduces thestatic charges of the paper pieces, paper fibers and electrostaticallypositively charged fibers so that positively charged fine ground fireretardant chemicals will adhere to the paper pieces, paper fibers andelectrostatically positively charged fibers.

Since settling reduction is the result of reducing the static charges inthe system to almost neutral. Settling will significantly decrease byincreasing the amount of antistatic constituent to a range of 0.002% to0.01% by weight of the sum of the paper and positive electrostatic fiberinput. However, because the fibers and paper pieces are not as far apartbecause of the additional antistat, density will slightly increase whenantistat is raised beyond that of the 0.001% to 0.002% antistat range.

EXAMPLE 1

A trial was made using 95% newspaper and 5% cardboard. The newspaper wasground in a shredder to a size of about 1″×1″. A precoat mixture wasthen added to the shredded newspaper, the precoat containing dimethyldistearyl ammonium chloride in the amount of 0.0015% by weight of thesum of the paper and positive electrostatic fiber input, combined withlimestone in the amount of 1.5% of the weight of paper and positiveelectrostatic fiber input. Partially ground cardboard in the amount of5% of the weight of paper and positive electrostatic fiber input wasthen added. These materials were fed in an air stream into a finish millalong with 10% of a finely ground fire retardant chemical, based on thetotal weight of the system.

The initial material had a density of 0.70 lbs/cu.ft. This material wasplaced in a 12″×12″×6″ high cardboard box in an atmosphere of 50%relative humidity and 70 degrees F. for a period of one month. Settlingwas 9% after one month.

Commercial cellulose, not containing the cardboard or antistat, underthe same conditions as above, had an initial density of 1.3 lb/cu.ft andsettled 16% over the same period.

EXAMPLE 2

A trial was made similar to Example 1 but the cardboard was firstcombined with the newspaper base before the addition of the limestoneantistat mixture. Under conditions similar to Example 1. Settling after30 days was 10% after one month and initial density was 0.70 lb./cu. ft.

EXAMPLE 3

A trial was made similar to Example 1 using 5% cardboard but theantistat was increased to 0.004% of the weight of paper and positiveelectrostatic fiber input. The initial material density increased to0.80 lbs./cu.ft. This material was placed in a 12″×12″×6″ high box in anatmosphere of 50% relative humidity and 70 degrees F. for a period ofone month. Settling was 3% after one month.

EXAMPLE 4

A trial was made similar to Example 1 but the antistat was increased to0.008% of the weight of paper and electrostatic fiber input. The initialmaterial density increased to 0.89 lbs/cu.ft. This material was placedin a 12″×12″×6″ high box in an atmosphere of 50% relative humidity and70 degrees F. for a period of one month. Settling was 2% after onemonth.

EXAMPLE 5

A trial was made similar to Example one but 5% sawdust was substitutedfor the cardboard. Antistat was added at 0.004% of the weight of paperand electrostatic fiber. The initial material density was 0.80lbs/cu.ft. This material was placed in a 12″×12″×6″ high box in anatmosphere of 50% relative humidity and 70 degrees F. for a period ofone mouth. Settling was 3% after one month.

EXAMPLE 6

A trial was made similar to Example 1 but 2% fiberglass was substitutedfor the cardboard used in Example 1. Under conditions similar to Example1, settling after 30 days was 10% and density was 0.75 lb./cu. ft.

EXAMPLE 7

A trial was made similar to Example 1 but 1% polyester fibers weresubstituted for the cardboard used in Example 1. Under conditionssimilar to Example 1, settling after 30 days was 8% and density was 0.78lb/cu. ft.

EXAMPLE 8

A trial was made similar to Example 2 but 1% polyester fibers weresubstituted for the cardboard used in Example 2. Under conditionssimilar to Example 2, settling after 30 days was 12% and density was0.77 lb/cu. ft.

While certain preferred embodiments of the present invention have beendisclosed in detail, it is to be understood that various modificationsmay be adopted without departing from the spirit of the invention orscope of the following claims.

What is claimed is:
 1. A method for manufacturing fire retardantcellulosic insulation comprising shredded cellulosic fibers and paperpieces coated with a mixture of limestone and an antistat and having afire retardant agent deposited on it, wherein the improvement comprises:(a) adding electrostatically, positively charged fibers and grinding thefibers, paper pieces and electrostatically, positively charged fibersafter adding the electrostatically, positively charged fibers; and (b)coating the fibers paper pieces with substantially 0.001% to 0.01% byweight antistat based on the weight of cellulosic fibers, paper piecesand electrostatically, positively charged fibers.
 2. A method inaccordance with claim 1, wherein the electrostatically, positivelycharged fibers are added in the amount of substantially 2% to 8% of theweight of the cellulosic fibers, paper pieces and electrostatically,positively charged fibers.
 3. A method in accordance with claim 1,wherein the electrostatically, positively charged fibers are fiberglassand are added substantially in the amount of 0.5% to 2% of the weight ofcellulosic fiber, paper pieces and electrostatically, positively chargedfibers.
 4. A method in accordance with claim 1 or claim 2 wherein theadded electrostatically, positively charged fibers comprise wood mulch.5. A method in accordance with claim 1 or claim 2 wherein the addedelectrostatically, positively charged fibers comprise ground cardboard.6. A method in accordance with claim 1 or claim 2 wherein the addedelectrostatically, positively charged fibers comprise sawdust.
 7. Animproved cellulosic insulation having reduced density and settling andcomprising: (a) shredded cellulosic fibers and paper pieces coated witha mixture of limestone and an antistat; (b) electrostatically positivelycharged fibers which have been ground with said cellulosic fibers tocause electrostatic charging of the electrostatically, positivelycharged fibers; and (c) fire retardant chemicals which are adhered onsaid shredded cellulosic fibers, paper pieces and electrostatically,positively charged fibers.
 8. An insulation in accordance with claim 7wherein the antistat is substantially 0.001% to 0.01% by weight based onthe weight of the cellulosic fibers, paper pieces and electrostatically,positively charged fibers.
 9. An insulation in accordance with claim 8wherein the paper fibers are electrostatically negative and are angledpredominantly from about 15% to perpendicular to the paper pieces. 10.An insulation in accordance with claim 8 wherein the electrostatically,positively charged fibers are in the amount of substantially 2% to 8% ofthe weight of the cellulosic fibers, paper pieces and electrostatically,positively charged fibers.
 11. An insulation in accordance with claim 8wherein the electrostatically, positively charged fibers comprise groundcardboard.
 12. An insulation in accordance wit claim 8 wherein theelectrostatically, positively charged fibers comprise wood mulch.
 13. Aninsulation in accordance with claim 8 wherein the electrostatically,positively charged fibers comprise sawdust.
 14. An insulation inaccordance with claim 11 or claim 12 or claim 13 wherein theelectrostatically, positively charged fibers are in the amount ofsubstantially 2% to 8% of the weight of the cellulosic fibers, paperpieces and electrostatically, positively charged fibers.
 15. Aninsulation in accordance with claim 8 wherein the electrostatically,positively charged fibers comprise fiberglass.
 16. An insulation inaccordance with claim 15 wherein the electrostatically, positivelycharged fibers are in the amount of substantially 0.5% to 2% of theweight of the cellulosic fibers, paper pieces and electrostatically,positively charged fibers.